Editing Great Observatories program (section)

== Synergies ==
[[File:Ssc2004-15b.jpg|thumb|upright=1.0|right|A labeled space image comparing views of a supernova remnant by three different Great observatories.]]

Aside from inherent mission capabilities (particularly sensitivities, which cannot be replicated by ground observatories), the Great Observatories program allows missions to interact for greater science return.  Different objects shine in different wavelengths, but training two or more observatories on an object allows a deeper understanding.

High-energy studies (in X-rays and gamma rays) have had only moderate imaging resolutions so far. Studying X-ray and gamma-ray objects with Hubble, as well as Chandra and Compton, gives accurate size and positional data. In particular, Hubble's resolution can often discern whether the target is a standalone object, or part of a parent galaxy, and if a bright object is in the nucleus, arms, or halo of a [[spiral galaxy]]. Similarly, the smaller aperture of Spitzer means that Hubble can add finer spatial information to a Spitzer image. Reported in March 2016, Spitzer and Hubble were used to discover the most distant-known galaxy, [[GN-z11]]. This object was seen as it appeared 13.4 billion years ago.<ref name="spitzer20160303">{{cite web |url=http://www.spitzer.caltech.edu/news/1861-feature16-04-Hubble-Team-Breaks-Cosmic-Distance-Record|title=Hubble Team Breaks Cosmic Distance Record|series=Spitzer Space Telescope|publisher=NASA|date=3 March 2016|access-date=14 December 2016}} {{PD-notice}}</ref><ref name="nasa20160825">{{cite web|url=http://www.jpl.nasa.gov/news/news.php?feature=6602|title=Spitzer Space Telescope Begins "Beyond" Phase |publisher=NASA|first=Elizabeth|last=Landau|date=25 August 2016|access-date=9 December 2016}} {{PD-notice}}</ref> ([[List of the most distant astronomical objects]])

Ultraviolet studies with Hubble also reveal the temporal states of high-energy objects. X-rays and gamma rays are harder to detect with current technologies than visible and ultraviolet. Therefore, Chandra and Compton needed long integration times to gather enough photons. However, objects which shine in X-rays and gamma rays can be small, and can vary on timescales of minutes or seconds. Such objects then call for followup with Hubble or the [[Rossi X-ray Timing Explorer]], which can measure details in angular seconds or fractions of a second, due to different designs. Rossi's last full year of operation was 2011.

The ability of Spitzer to see through dust and thick gases is good for galactic nuclei observations. Massive objects at the hearts of galaxies shine in X-rays, gamma rays, and radio waves, but infrared studies into these clouded regions can reveal the number and positions of objects.

Hubble, meanwhile, has neither the [[field of view]] nor the available time to study all interesting objects. Worthwhile targets are often found with ground telescopes, which are cheaper, or with smaller space observatories, which are sometimes expressly designed to cover large areas of the sky. Also, the other three Great Observatories have found interesting new objects, which merit diversion of Hubble.

One example of observatory synergy is [[Solar System]] and [[asteroid]] studies. Small bodies, such as small [[Natural satellite|moons]] and asteroids, are too small and/or distant to be directly resolved even by Hubble; their image appears as a [[diffraction]] pattern determined by brightness, not size. However, the minimum size can be deduced by Hubble through knowledge of the body's [[albedo]]. The maximum size can be determined by Spitzer through knowledge of the body's temperature, which is largely known from its orbit. Thus, the body's true size is bracketed. Further [[spectroscopy]] by Spitzer can determine the chemical composition of the object's surface, which limits its possible albedos, and therefore sharpens the low size estimate.

At the opposite end of the [[cosmic distance ladder]], observations made with Hubble, Spitzer and Chandra have been combined in the [[Great Observatories Origins Deep Survey]] to yield a multi-wavelength picture of [[galaxy formation and evolution]] in the early [[Universe]].

{{wide image|File:Center of the Milky Way Galaxy IV – Composite.jpg|1000px|[[Milky Way]] [[Galactic Center]] as seen by  the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory}}